1) Field of the Invention
The present invention relates to a half-transmission and half-reflection type color liquid crystal display device which comprises a reflection area having a reflection layer and a color filter, and a transmission area having a color filter without the reflection layer, in each pixel of Red (R), Green (G), and Blue (B) color, and a manufacturing method of the same.
2) Description of the Related Art
FIG. 9 is a cross section of a conventional color liquid crystal display device of the half-transmission and half-reflection type. As shown in FIG. 9, in a reflection area 100 of each pixel, a reflection layer 2 is provided on a glass substrate 1b as a first substrate. An overcoat layer 3a is formed on the glass substrate 1b, and red, green, or blue color filters 4a, 4b, and, 4c are formed on the overcoat layer 3a. On the other hand, the reflection layer 2 is not provided in the transmission area 101 of each pixel.
FIGS. 10A to 10F show process flow charts of a manufacturing process of the color liquid crystal display device shown in FIG. 9. At first, as shown in FIG. 10A, a 0.1 xcexcm-thick metal film of Al or Ag and the like that turns into the reflection layer 2 is formed on the glass substrate 1b by means of sputtering or vacuum evaporation. Then, a positive photo resist 9 is coated on the surface of the metal film.
As shown in FIG. 10B, the photo resist 9 is exposed by using a photo mask 10 that has desired patterns. Then, the development and etching are performed. As shown in FIG. 10C, the metal film in the transmission area 101 is removed so that the metal film remains only in the reflection area 100, thus the reflection layer 2 is formed. As shown in FIG. 10D, the remaining photo resist 9 is removed.
As shown in FIG. 10E, the overcoat layer 3a with a thickness of 0.02 xcexcm of SiO2 or the like is formed on all over the surface of the substrate by sputtering. As shown in FIG. 10F, pigment dispersion type color filters 4a, 4b, and 4c having a thickness of around 0.7 xcexcm are formed on the surface of the overcoat layer 3a. Furthermore, a transparent electrode pattern 5b and an alignment layer 6b are deposited sequentially on the color filters 4a, 4b, and 4c. The color liquid crystal display device having the structure shown in FIG. 9 is obtained by injecting a liquid crystal 7 in between the substrate and a facing substrate 1a having the transparent electrode pattern 5a and the alignment layer 6a, after the two substrates are panel aligned.
Incidentally, in the half-transparent and half-reflection type color liquid crystal display device, it is known, in Japanese Patent Laid-Open No. 2001-281648, that the colors displayed by transmission lights are lighter in color than the colors displayed by reflection lights. This phenomenon is caused because the number of times the light passes through the color filters is different in the reflecting area 100 and in the transmission area 101.
Namely, as shown in FIG. 9, in the reflection area 100, an outside light R, which enters from the front side of the panel, reaches the reflection layer 2, after passing through the facing substrate 1a, the liquid crystal 7, and the color filters 4a, 4b, and, 4c, then returns through the color filters 4a, 4b, and 4c, the liquid crystal 7, and the facing substrate 1a, after reflecting at the reflection layer 2. This means that the light R passes through the color filters twice in the reflection area 100.
On the other hand, in the transmission area 101, the transmission light T, which is radiated from a backlight, for example, enters from the backside of the panel and passes through the color filters 4a, 4b, and, 4c, the liquid crystal 7, and the facing substrate 1a. Therefore, the transmission light T passes through the color filters 4a, 4b, and, 4c only once. Therefore, the display by the reflection light becomes deeper than the display by the transmission light, because the reflection light passes through the color filters more often than the transmission light passes through the color filters.
The Japanese Patent Laid-Open No. 2001-281648 proposes that the thickness of the color filter in the transmission area should be about twice as thick as the thickness of the color filter in the reflection area. If this rule is followed, the chromatic variance between the reflection display and the transmission display caused by the difference of times the lights pass through the color filters is reduced. Further, the Japanese Patent Laid-Open No. 2001-281648 proposes a method of forming different color filters separately in the reflection area and in the transmission area. Each color filter has different color purity. The Japanese Patent Laid-Open No. 2001-281648 also proposes a structure comprising two layers in only the transmission area where each layer has different color purity.
According to the art disclosed in the Japanese Patent Laid-Open Publication No. 2001-281648, the thickness of the color filter in the reflection area is 0.8 xcexcm, and the thickness of the reflection layer is 0.2 xcexcm. Namely, the thickness of the reflection layer which is formed by conventional manufacturing methods such as sputtering or vacuum evaporation is around 0.2 xcexcm, and the thickness of the color filter required for the color liquid crystal display device is around 0.8 xcexcm.
Therefore, as shown in FIG. 1 of the Japanese Patent Laid-Open Publication No. 2001-281648, if the color filter is formed ranging from the reflection area to the transmission area by a single layer, the thickness of the color filter in the reflection area is 0.8 xcexcm and the thickness of the color filter in the transmission area is 1 xcexcm. This means that the difference between the thickness of the color filter in the reflection area and the thickness of the color filter in the transmission area is only 0.2 xcexcm. Thus, the ratio of the thicknesses of the color filter in the transmission area and that in the reflection area is only 1:0.8=1.25, and it does not satisfy a targeted ratio of approximately 2.
Therefore, in the Japanese Patent Laid-Open Publication No. 2001-281648, in order to make the deepness of the color filter in the transmission area approximately twice as deep as the deepness of the color filter in the reflection area, not only changing the thickness of the color filters, but also forming color filters having different color purities in the reflection area and in the transmission area (in FIG. 3 of Japanese Patent Laid-Open Publication No. 2001-281648), or a two-layered structure comprising two different color filters, each having different color purity (in FIG. 2 of Japanese Patent Laid-Open Publication No. 2001-281648), are proposed.
However, in order to differentiate the color purity of the color filter in the transmission area from the color purity of the color filter in the reflection area, it is necessary to form the color filter in either one area first, the color filter in the other area must be formed later. Also, in order to make the color filter in the transmission area the two-layered structure, it is necessary to form a first color filter only in the transmission area at first, then a second color filter layer should be formed covering both the transmission area and the reflection area. In any case, in the process of forming color filters, at least two steps are required for each color, which means six steps are required in total, resulting in a cost increase due to the increase of the production steps.
It is an object of the present invention to overcome and resolve the aforementioned problems of the prior art, and provide a half-transmission and half-reflection type color liquid crystal display device that can be manufactured by one process per color
The color liquid crystal display device according to one aspect of the present invention comprises a first substrate; a second substrate facing the first substrate; a liquid crystal layer enclosed between the first substrate and the second substrate; a reflection layer laminated on the first substrate, the reflection layer having a reflection area that reflects a light that comes in from the second substrate; and a transmission area that allows a light coming in from the first substrate to pass through to the second substrate; an adjustment film laminated on the reflection area of the reflection layer, the adjustment film having permeability to light; and a color filter laminated on both the adjustment film and the transmission area.
The color liquid crystal display device according to another aspect of the present invention comprises a first substrate; a second substrate facing the first substrate; a liquid crystal layer enclosed between the first substrate and the second substrate; a reflection layer laminated on the first substrate, the reflection layer having a reflection area that reflects a light coming in from the second substrate; and a transmission area that allows a light coming in from the first substrate to pass through to the second substrate; an adjustment film laminated between the reflection area of the reflection layer and the first substrate, the adjustment film having permeability to light; and a color filter laminated on both the reflection layer of the reflection area and the transmission area.
The method of manufacturing a color liquid crystal display device according to still another aspect of the present invention comprises forming a first film on a first substrate in such a manner that the first film reflects a light coming in from a second substrate that faces the first substrate; forming a second film having permeability to light on the first film; selectively removing portions of the first film and the second film to form a transmission area through which the light coming in from the first substrate can pass through to the second substrate and leaving portions of the first film and the second film as a reflection layer and an adjustment film respectively in a reflection area where the light coming in from the second substrate is reflected; forming a color filter on both the adjustment film and the transmission area; panel aligning the first substrate and the second substrate; and enclosing a liquid crystal layer between the first substrate and the second substrate.
The method of manufacturing a color liquid crystal display device according to still another aspect of the present invention comprises selectively forming an adjustment film on the first substrate; forming a reflection layer on the adjustment film, the reflection layer reflecting light coming in from a second substrate that is facing the first substrate; forming a color filter covering the reflection layer and a transmission area in which the light coming in from the first substrate is transmitted to the second substrate; panel aligning the first substrate and the second substrate; and enclosing a liquid crystal layer between the first substrate and the second substrate.
These and other objects, features and advantages of the present invention are specifically set forth in or will become apparent from the following detailed descriptions of the invention when read in conjunction with the accompanying drawings.